Re: Stereo and AMP Power question????
Wow! More than 30 years in the biz and I've never seen .707 X.707. You have to be kidding me. If you need to be that right, then go for it... Your ego, over doing the right thing... Knock yourself out. Sucks that you are willing to be right at the expense of someone looking for help.
ve3rpm:
I do not know what business you are in, but it is not electrical (or electronic) engineering. Power is Voltage(RMS)*current(RMS). Peak power is peak volatge * peak current. The relationship for RMS is peak*0.707=RMS. This is true for both current and voltage. Thus the 0.707*0.707 mentioned above. My business is electrical engineering. I have a masters degree in electrical engineering and have been doing this since 1977. In addition, I teach electronics as a side-line business.
As far as Nate's original concern, 40 amps will be a bit much on any battery for 5 hours. Fortunately, you will not be drawing 40 amps continuously. Regarless of how loud you crank your system, there will be some relatively quiet intervals that will draw less than 40 amps. My seat-of-the pants guess is that you will be drawing closer to 25 or 30 amps on an average. If that 120 reserve is amp-hours, you will get about 3 hours of play time (or would from a brand new fully charged battery). Age and discharge cycles will reduce that substantially. Personally, I would get a big group 31 deep cycle battery and use that to power the stereo. Unless you are running the motor at near full throttle, you will not get much charging from the motor. You will need to charge the battery every time you dock it (or trailer it home) or the battery will not have a very long life. By that I mean charge it immediately after every outing.
TerryMSU
